Sometimes it seems like bitcoin is worth whatever Tesla founder Elon Musk and star stock picker Cathie Wood say it is. But what happens if they disagree?

A host of crypto assets took a hit yesterday when Musk said the electric car company would stop accepting bitcoin as payment until it is produced using more sustainable sources of energy. “We are concerned about rapidly increasing use of fossil fuels for bitcoin mining and transactions, and especially coal, which has the worst emissions of any fuel,” Musk said on Twitter. The mercurial entrepreneur said Tesla, which makes a large chunk of its profit from selling carbon tax credits, wouldn’t sell its bitcoin holdings and would investigate other crypto assets that use less energy.

Bitcoin fell about 8% in early morning trading to $52,147, its lowest price on a closing basis since April 26, according to Coindesk data.

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Elon Musk said Tesla has suspended vehicle purchases using Bitcoin due to concerns over mining emissions.